Conventional computer networks typically have at least one common data storage device for central data storage, such as the Hp SureStore Virtual Array 7100 by Hewlett Packard. The SureStore VA 7100 is one exemplary redundant array of independent discs (RAID) that employs a plurality of independent discs (e.g., fiber channel hard drives) in combination for fault tolerance and performance considerations. Conventional RAID arrays and other devices employing an array of data storage media suffer from inconsistent block formatting among the data storage media within the array. It should be appreciated that block formatting as utilized in the present specification refers to formatting the block size and/or block data content of a data storage medium, and can be broadly interpreted to include partitioning and/or data formatting.
Specifically, arrays of data storage media for storing data each have a desired system block format. A specific block format is required to allow an operating system to appropriately define where data files stored on the array of data storage media begin and end. Conventional data storage media, however, are typically manufactured having pre-determined block formats that may be different from the desired system block format. For example, standard 18 GB hard drives (part no. ST318451F) manufactured by Seagate come with a standard 512 byte block format. The Hewlett Packard SureStore VA 7100, however, requires a 520 byte block format to provide an eight byte checksum per 512 byes of stored data, which is used for various fault detection and error correction procedures. Thus, 520-byte data storage media have to be specially manufactured for systems with a non-standard block format, which adds to the cost of building the system. A previous solution (Auto Format) for this problem was described in U.S. Pat. No. 6,681,308, titled “Method for Automatically Converting Block Size and Formatting Backend Fibre Channel Disks in an Auto-Inclusive Storage Array Environment.”
One option to avoid the lengthy format time associated with Auto Formatting (SCSI format), of a drive, is to use a method known as “fast format,” wherein only a format template (in the present embodiment, 512 to 520) for a write block is changed, with minimal or no formatting being performed of the blocks. Specifically, no blocks are reformatted until a “write” operation is to be performed on the given block. When a “write” operation is called, then a 520 format template is used to reformat the particular block. The assumption for making the fast format method viable is that each block will be written to before being read from. One “fast format” method is provided by Seagate drives, which perform minimal drive preparation, by changing only the template for the write block boundaries from 512 to 520, and then returns as if the full format had been completed. Such a fast format operation means that a storage array such as the VA7100/7400/7410/7110 could include and use this disk almost instantly as compared with the introduction of a new 512-byte block drive using a standard format technique, wherein each block is individually formatted prior to use of the storage medium. Unfortunately, this fast formatting has left the disk in a state where the drive reports a 520-byte block format, but all blocks are actually still formatted to 512-byte block size. But, the storage array is not aware of this new expectation and may read from blocks before writing to them. Reading before writing can cause lengthy retries and accumulated errors that can lead to false failure prediction.
Thus, a need exists for a method of integrating fast formatted media into an array of data storage media.